Ah...well in that case, your position on the issue makes perfect sense. If the customer bothered calling that late in the first place I think its safe to assume they're awake and trying to solve their problem without your IT support until they get a call back. Is there some kind of standard procedure for how long max to call a customer back? You know, like if they call do you only have like 30 min to respond? or something like that. Me, in my judgment I probably wouldn't call after 10:45. If they're sleeping they don't have to answer, and if they DO and are pissed someone is calling that late, you apologize and hang up. No big deal right?